332 Races of Entamoeba histolytica 
hardened after fixation, and numerous grades of alcohol employed. In 
the following experiment, the gelatine was hardened in formol-alcohol 
(formol (40 % formaldehyde) and absolute alcohol, equal parts). As will 
be seen this procedure had no visible efiect on the dimensions of the cyst. 
Measurements were made in each grade of alcohol used. 
Medium in wlaich cyst was examined 
Gelatine jelly (living cyst) 
Dimensions 
14-25p X 12-75p 
Fixative (after 5 mins.) 
15p 
X 12p 
Fixative (after 40 mins.) 
15p 
X 12p 
Formol-alcohol (after 2| hrs.)... 
15p 
X 12p 
Alcohols 35 %, 20 %, 10 % ... 
15p 
X 12p 
Distilled water ... 
15p 
X 12p 
Haemalum (15 mins.) ... 
Tap water . 
15p 
X 12p 
Alcohols 10 %, 20 %, 35 %, 50 %, 
70%, 90% 
15p 
X 12p 
Absolute alcohol 
15p 
X 12p 
Xylol . 
13-5p 
X 10-5p 
Balsam (after 20 mins.) 
13-5p 
X 10-5p 
It will be apparent from the foregoing figures that the dimensions of 
the cyst underwent no change until its final transference to xylol and 
balsam. (There was a slight change in shape, but not in size, in the 
fixative.) Here again the final reduction in size was clearly seen to be 
due to the disappearance of the cyst wall in the clearing and mounting 
media. 
It will be noticed that in Expts. 1 and 3 the actual loss in diameter 
observed was T5/x, whilst in Expt. 2 there was a loss of 2*25 /a in the 
longer, and of 3 p, in the shorter diameter of the cyst. If the diminution in 
size had been due only to the disappearance of the cyst wall, there should 
have been only a loss of 1 p-T2p in the diameters. In Expt. 2 the greater 
reduction was clearly due to the shrinkage of the protoplasmic contents; 
and it seems reasonable to suppose that the slightly greater loss than 
we expected in the other two experiments was due to the same cause. 
It will be remembered that in our earlier observations on the mean size 
of 500 cysts in saline solution and in balsam, we actually found a differ¬ 
ence in average diameter of only about 1 p. We think that this was 
probably due to the fact that the fixed cysts were very thoroughly 
hardened in alcohol before staining and mounting, in order to prevent 
shrinkage as far as possible: and, in measuring these cysts subsequently, 
we rejected all those which showed signs of shrinkage. 
